Stents with Profiles for Gripping a Balloon Catheter and Molds for Fabricating Stents

ABSTRACT

A radially expandable stent can comprise a proximal section tapering inward to a proximal end of the stent and a distal section tapering inward to a distal end of the stent. The tapered sections can be adapted to improve the attachment of the stent to the delivery system and to facilitate the delivery of the mounted stent into and through a bodily lumen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of application Ser. No. 12/772,893,filed May 3, 2010, now U.S. Pat. No. 8,393,887, which is a divisional ofapplication Ser. No. 12/101,044, filed Apr. 10, 2008, now U.S. Pat. No.7,708,548, which is a divisional of 11/105,004, filed Apr. 12, 2005, nowU.S. Pat. No. 7,381,048, all of which applications are incorporatedherein by reference.

TECHNICAL FIELD

This invention relates generally to stent delivery apparatuses, and moreparticularly, but not exclusively, to a stent for gripping a ballooncatheter and a mold for fabricating the stent.

BACKGROUND

Blood vessel occlusions are commonly treated by mechanically enhancingblood flow in the affected vessels, such as by employing a stent. Stentsact as scaffoldings, functioning to physically hold open and, ifdesired, to expand the wall of affected vessels. Typically stents arecapable of being compressed, so that they can be inserted through smalllumens via catheters, and then expanded to a larger diameter once theyare at a desired location. Examples in the patent literature disclosingstents include U.S. Pat. No. 4,733,665 issued to Palmaz, U.S. Pat. No.4,800,882 issued to Gianturco, and U.S. Pat. No. 4,886,062 issued toWiktor.

Conventionally, stents are delivered to the desired location by crimpingthe stent tightly onto a balloon catheter and transporting the crimpedstent/balloon catheter combination to the desired location through apatient's vasculature. Alternatively or in addition to the crimping, theballoon catheter is expanded to contact the inner diameter of the stent.At the desired location, the balloon catheter is expanded, therebyexpanding the stent to contact the inner diameter of the patient'sartery. The balloon catheter is then deflated and removed from thevasculature.

Since the stent and catheter travel through the patient's vasculature,the stent must have a small diameter so that it can pass through smalllumens of the patient's vasculature. Secure attachment to the catheteris desirable so that the stent does not prematurely detach from thecatheter. The stent should also be sufficiently flexibility to travelthrough curvatures in the patient's vasculature.

However, conventional crimping techniques can be uneven, leading tosharp edges on the crimped stent that can damage or get caught on thepatient's vasculature during delivery. Further, crimping can decreaseflexibility of the stent, making it hard to deliver the stent throughcurvatures in the patient's vasculature.

If the balloon catheter is expanded before delivery, the ballooncatheter may cause excessive expansion of the stent, thereby making ithard to transport the stent through the patient's vasculature (e.g.,cross tight lesions). Further, expansion of the balloon catheter cancause the distal and proximal ends of the stent to expand further thanthe rest of the stent, causing the distal and proximal ends to haveupward tapered edges that can get caught in the patient's vasculature,thereby decreasing deliverability.

Accordingly, improved methods and devices are desirable for gripping astent to a balloon catheter that reduce or eliminated the deficienciesmentioned above.

SUMMARY

Briefly and in general terms, the present invention is directed to astent and mold for a stent. In aspects of the present invention, a stentcomprises a proximal section tapering inward to a proximal end of thestent and a distal section tapering inward to a distal end of the stent,the tapered sections being adapted to improve the attachment of thestent to the delivery system and to facilitate the delivery of themounted stent into and through a bodily lumen.

In other aspects of the present invention, a mold comprises a moldmember having a projection into a proximal section of a mold bore of themold member, the projection configured to mold a tapered section at aproximal end of a stent mounted on a delivery system, the taperedsection adapted to improve the attachment of the stent to the deliverysystem and facilitate the delivery of the mounted stent into and througha bodily lumen.

In other aspects of the present invention, a mold comprises a moldmember comprising a mold bore configured to mold a stent mounted on adelivery system. The mold bore has a proximal section tapering inward toa proximal end of the mold bore and a distal section tapering inward toa distal end of the mold bore. The tapered sections are adapted to moldtapered sections of the stent that improve the attachment of the stentto the delivery system and that facilitate the delivery of the mountedstent into and through a bodily lumen.

The features and advantages of the invention will be more readilyunderstood from the following detailed description which should be readin conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following figures, wherein likereference numerals refer to like parts throughout the various viewsunless otherwise specified.

FIG. 1 is an illustration of a stent.

FIG. 2 is a diagram illustrating a stent installed on a balloon catheterusing the mold of FIG. 7.

FIG. 3 is a diagram illustrating a stent formed using the mold of FIG.9.

FIG. 4 is a diagram illustrating a stent formed using the mold of FIG.10.

FIG. 5 is a diagram illustrating a stent formed using the mold of FIG.11.

FIG. 6 is a diagram illustrating a mold according to an embodiment ofthe invention.

FIG. 7 is a diagram illustrating a cross section of the mold of FIG. 6.

FIG. 8 is a diagram illustrating a mold according to another embodimentof the invention.

FIG. 9 is a diagram illustrating a cross section of the mold of FIG. 8.

FIG. 10 is a diagram illustrating a cross section of a mold accordinganother embodiment of the invention.

FIG. 11 is a diagram illustrating a cross section of a mold accordinganother embodiment of the invention.

FIG. 12 is a flowchart illustrating a method of gripping a stent on acatheter according to an embodiment of the invention.

DETAILED DESCRIPTION

The following description is provided to enable any person havingordinary skill in the art to make and use the invention, and is providedin the context of a particular application and its requirements. Variousmodifications to the embodiments will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other embodiments and applications without departing from thespirit and scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown, but is to be accordedthe widest scope consistent with the principles, features and teachingsdisclosed herein.

The term “implantable medical device” is intended to includeself-expandable stents, balloon-expandable stents, stent-grafts, andgrafts. The structural pattern of the device can be of virtually anydesign. A stent, for example, may include a pattern or network ofinterconnecting structural elements or struts. FIG. 1 depicts an exampleof a three-dimensional view of a stent 10. The stent may have a patternthat includes a number of interconnecting elements or struts 15. Theembodiments disclosed herein are not limited to stents or to the stentpattern illustrated in FIG. 1. The embodiments are easily applicable toother patterns and other devices. The variations in the structure ofpatterns are virtually unlimited. As shown in FIG. 1 the geometry orshape of a stent varies throughout its structure.

In some embodiments, a stent may be formed from a tube by laser cuttingthe pattern of struts in the tube. The stent may also be formed by lasercutting a polymeric or metallic sheet, rolling the pattern into theshape of the cylindrical stent, and providing a longitudinal weld toform the stent. Other methods of forming stents are well known andinclude chemically etching a sheet and rolling and then welding it toform the stent. A polymeric or metallic wire may also be coiled to formthe stent. The stent may be formed by injection molding of athermoplastic or reaction injection molding of a thermoset polymericmaterial. Filaments of the compounded polymer may be extruded or meltspun. These filaments can then be cut, formed into ring elements, weldedclosed, corrugated to form crowns, and then the crowns welded togetherby heat or solvent to form the stent. Lastly, hoops or rings may be cutfrom tubing stock, the tube elements stamped to form crowns, and thecrowns connected by welding or laser fusion to form the stent.

Additionally, an implantable medical device may be configured to degradeafter implantation by fabricating the device either partially orcompletely from biodegradable polymers. Polymers can be biostable,bioabsorbable, biodegradable, or bioerodable. Biostable refers topolymers that are not biodegradable. The terms biodegradable,bioabsorbable, and bioerodable, as well as degraded, eroded, andabsorbed, are used interchangeably and refer to polymers that arecapable of being completely eroded or absorbed when exposed to bodilyfluids such as blood and can be gradually resorbed, absorbed, and/oreliminated by the body.

Furthermore, a biodegradable device may be intended to remain in thebody for a duration of time until its intended function of, for example,maintaining vascular patency and/or drug delivery is accomplished. Forbiodegradable polymers used in coating applications, after the processof degradation, erosion, absorption, and/or resorption has beencompleted, no polymer will remain on the stent. In some embodiments,very negligible traces or residue may be left behind. The duration istypically in the range of six to twelve months.

Representative examples of polymers that may be used to fabricateembodiments of implantable medical devices disclosed herein include, butare not limited to, poly(N-acetylglucosamine) (Chitin), Chitosan,poly(3-hydroxyvalerate), poly(lactide-co-glycolide),poly(3-hydroxybutyrate), poly(4-hydroxybutyrate),poly(3-hydroxybutyrate-co-3-hydroxyvalerate), polyorthoester,polyanhydride, poly(glycolic acid), poly(glycolide), poly(L-lacticacid), poly(L-lactide), poly(D,L-lactic acid), poly(D,L-lactide),poly(L-lactide-co-D,L-lactide), poly(caprolactone),poly(L-lactide-co-caprolactone), poly(D,L-lactide-co-caprolactone),poly(glycolide-co-caprolactone), poly(trimethylene carbonate), polyesteramide, poly(glycolic acid-co-trimethylene carbonate),co-poly(ether-esters) (e.g. PEO/PLA), polyphosphazenes, biomolecules(such as fibrin, fibrinogen, cellulose, starch, collagen and hyaluronicacid), polyurethanes, silicones, polyesters, polyolefins,polyisobutylene and ethylene-alphaolefin copolymers, acrylic polymersand copolymers other than polyacrylates, vinyl halide polymers andcopolymers (such as polyvinyl chloride), polyvinyl ethers (such aspolyvinyl methyl ether), polyvinylidene halides (such as polyvinylidenechloride), polyacrylonitrile, polyvinyl ketones, polyvinyl aromatics(such as polystyrene), polyvinyl esters (such as polyvinyl acetate),acrylonitrile-styrene copolymers, ABS resins, polyamides (such as Nylon66 and polycaprolactam), polycarbonates, polyoxymethylenes, polyimides,polyethers, polyurethanes, rayon, rayon-triacetate, cellulose, celluloseacetate, cellulose butyrate, cellulose acetate butyrate, cellophane,cellulose nitrate, cellulose propionate, cellulose ethers, andcarboxymethyl cellulose. Additional representative examples of polymersthat may be especially well suited for use in fabricating embodiments ofimplantable medical devices disclosed herein include ethylene vinylalcohol copolymer (commonly known by the generic name EVOH or by thetrade name EVAL), poly(butyl methacrylate), poly(vinylidenefluoride-co-hexafluoropropene) (e.g., SOLEF 21508, available from SolvaySolexis PVDF, Thorofare, N.J.), polyvinylidene fluoride (otherwise knownas KYNAR, available from ATOFINA Chemicals, Philadelphia, Pa.),ethylene-vinyl acetate copolymers, poly(vinyl acetate),styrene-isobutylene-styrene triblock copolymers, and polyethyleneglycol.

In addition, a device may be made of a metallic material or an alloysuch as, but not limited to, cobalt chromium alloy (ELGILOY), stainlesssteel (316L), high nitrogen stainless steel, e.g., BIODUR 108, cobaltchrome alloy L-605, “MP35N,” “MP20N,” ELASTINITE (Nitinol), tantalum,nickel-titanium alloy, platinum-iridium alloy, gold, magnesium, orcombinations thereof. “MP35N” and “MP20N” are trade names for alloys ofcobalt, nickel, chromium and molybdenum available from Standard PressSteel Co., Jenkintown, Pa. “MP35N” consists of 35% cobalt, 35% nickel,20% chromium, and 10% molybdenum. “MP2ON” consists of 50% cobalt, 20%nickel, 20% chromium, and 10% molybdenum.

As discussed above, delivery of a stent is facilitated by a secureattachment of the stent to a delivery system and by flexibility of thestent. A small profile stent (crimped tightly) with a small stentdiameter allows for secure attachment and eases transport through narrowlumen passages. However, decreasing a profile of a stent also decreasesflexibility of the stent. Conversely, a larger profile stent (expandedstent) with a large stent diameter allows for greater flexibility.However, a large profile makes transport through narrow lumen passagesmore difficult.

The negative effects on delivery of a small and large profile can bereconciled by using a stent having both large and small profilesections. The small profile sections facilitate secure attachment, whilethe large profile sections facilitate flexibility. Furthermore, a smallprofile section at or proximate to a stent end that is a leading end oredge during delivery may be particularly helpful in facilitatingdelivery. Various embodiments of implantable medical devices, such asstents, having at least these characteristic are disclosed herein.

Certain embodiments of an implantable medical device, such as a radiallyexpandable stent, mounted on a delivery system may include a proximalsection tapering inward to a proximal end of the stent and a distalsection tapering inward to a distal end of the stent. The taperedsections may be adapted to improve the attachment of the stent to thedelivery system. Additionally, the tapered section may facilitate thedelivery of the mounted device into and through a bodily lumen.

Facilitating delivery may include facilitating smooth communication ofdevice through a lumen without substantially limiting the ability ofdevice to bend around curvatures in the lumen. Facilitating deliveryalso may include improving a grip or attachment of the device on thedelivery system since. A tapered portion of a device may tend tostrengthen a grip of the device on the delivery system. Thus a taperedsection may inhibit or prevent disengagement of the device from thedelivery system.

In one embodiment, at least a portion of the stent may have across-section that is circular or substantially circular. A deliverysystem may be, for example, a balloon catheter for delivering a stent.

As an illustration, FIG. 2 depicts an axial cross section of a stent 220having tapered sections 230 and 240 at a distal end and a proximal end,respectively. Stent 220 may be installed on balloon catheter 210 using amold 600 in FIG. 7. Installed stent 220 has a profile in which proximalsection 230 and distal section 240 of stent 220 exhibit an inward taper,instead of straight or outward taper outwards, as with conventionalstents.

Accordingly, stent 220 can more easily travel through a patient'svasculature during delivery and is less likely to get caught in ordamage the vasculature. Further, since the majority of stent 220 has anexpanded profile, stent 220 can still track curvatures in thevasculature.

Additionally, the profile also causes stent 220 to “hug” or grip ballooncatheter 210, thereby increasing the ability of stent 220 to staymounted to the balloon catheter during delivery (until balloon 210 isdeflated).

In some embodiments, an implantable medical device, such as a stent,mounted on a delivery system may have a proximal section tapering inwardto a proximal end of the stent and a distal section tapering inward to adistal end of the stent. The tapered sections may be adapted to improvethe attachment of the stent to the delivery system and to facilitate thedelivery of the mounted device into and through a bodily lumen.

In one embodiment, a device may have profile that tapers inwardrelatively uniformly between the proximal section and the distalsection. Thus, the mounted stent may have an “arrow-like” shape. As anillustration, FIG. 3 depicts a stent 300 having a proximal section 310that is tapered inward toward a proximal end. Stent 300 also has asection 320 that tapers inward relatively uniformly from the proximalsection to a distal end to adopt an arrow-like shape. Stent 300 may beinstalled on a balloon catheter using a mold 800 in FIG. 9.

As indicated above, a small profile at a leading end or edge of a stentis particularly advantageous. To facilitate delivery, the distal end maybe a leading edge during delivery. A “leading edge” is the edge of stentthat faces the direction of travel during implantation of the stent.

In another embodiment, the proximal section may taper inward relativelyuniformly from an intermediate point between the proximal end and thedistal end to the proximal end. The distal section may taper inwardrelatively uniformly from the intermediate point to the distal end.

As an illustration, FIG. 4 depicts a stent 410 having a proximal section420 and a distal section 430 that taper inward relatively uniformly froman intermediate point 440. Stent 410 has a diameter that graduallyincreases from a minimum value at the proximal and distal ends to amaximum value at intermediate point 440. Intermediate point 440, forexample, may be approximately midway between the proximal and distalends of the stent. Stent 410 may be installed on a balloon catheterusing a mold 1000 in FIG. 10.

In one embodiment, a diameter of a stent that is about 6 mm long andabout 0.041 inches in diameter at its midpoint can have a diameter atthe distal and proximal ends between about 0.037 inches to about 0.038inches.

The profile of stents 220, 300, and 410 facilitate a firm attachment ofthe stents to a balloon catheter, while maintaining flexibility.Further, the stents may travel more easily through tight lumens due tothe small diameter at the ends as compared to conventional stents.Further, the stents are less likely to get caught or damage thepatient's vasculature because the stents lack upwardly tapered ends asconventional stents may have after balloon catheter expansion.

In further embodiments, an implantable medical device, such as a stentmounted on a delivery system may include a section having across-section that oscillates in size between a proximal section and adistal section. The oscillating cross section may be adapted to improveflexibility during delivery of the mounted stent. Such a stent may havea “wave-like” profile with peaks and troughs.

The section of a stent having a wave-like profile may have at least onenarrow region alternating with at least one wide region. At least aportion of the at least one narrow region is in contact with a surfaceof the delivery system. In addition, at least a portion of the at leastone wide region may not be in contact with the surface of the deliverysystem. Thus, narrow regions may allow the stent to grip a ballooncatheter. In addition, the wide regions allow the stent to flex and bendas the mounted stent passes through curved and/or narrow vasculature.

FIG. 5 depicts a stent 520 with an oscillating cross section formedusing mold 1100 in FIG. 11. Stent 520 has a wave-like shape or profile,which provides the advantages mentioned above. It will be appreciated byone of ordinary skill in the art that stent 520 can take other waveprofiles. For example, the profile can include additional crests andtroughs and/or can be symmetrical or asymmetrical.

Various embodiments of a mold for implantable medical devices that aredescribed herein may include a mold member having a mold bore configuredto mold a stent mounted on a delivery system. The mold member may moldthe stent after the delivery system expands an outer surface of thestent onto at least a portion of an inner surface that defines the moldbore.

A mold member may be composed of more than one piece. In someembodiments, the mold member may be composed of two halves. Each halfmay have a device-holding groove. The grooves may be configured to formthe mold bore when the two halves are joined. In one embodiment, themold may include a lock adapted to inhibit or prevent opening of themold during molding of the device.

In one embodiment, a mold member may have a projection into a proximalsection of a mold bore of the mold member. The projection may beconfigured to mold a tapered section at a proximal end of an implantablemedical device, such as a stent, mounted on a delivery system. Thetapered section, as described above, may be adapted to improve theattachment of the stent to the delivery system and facilitate thedelivery of the mounted stent into and through a bodily lumen.

In another embodiment, the mold member may have a second projection intoa distal section of a mold bore of the mold member for molding a taperedsection into a distal end of a stent. In some embodiments, theprojection may include a cylindrical member having an annulus disposedwithin the mold.

As an illustration, FIG. 6 is a diagram illustrating a mold member ormold 600 according to an embodiment of the invention that may, forexample, mold stent 220 in FIG. 2. Mold 600 takes a split mold shape andhas two halves: 610 a and 610 b, each having a groove 620 a and 620 b,respectively, running down a longitudinal axis of halves 610 a and 610b. Halves 610 a and 610 b are coupled together via a hinge 615 thatenables mold 600 to open and close via rotation of one half with respectto the other half. Hinge 615 ensures proper alignment of the halves 610a and 610 b when mold 600 is closed. Grooves 620 a and 620 b areconfigured to receive and hold a balloon catheter 210 (FIG. 2) and astent 220 (FIG. 2) in place.

Grooves 620 a and 620 b form a mold bore 625 (FIG. 7) through mold 600when mold 600 is closed, that has a diameter greater than the diameterof stent 220 (e.g., from about 0.003 inches greater to about 0.048inches greater for a stent which is approximately 0.045 inch indiameter). Grooves 620 a and 620 b each include two half washers 650spaced apart to approximately match the length of stent 220. Halfwashers 650 project or extend into grooves 620 a and 620 b.

When balloon catheter 210 is expanded (via internal air pressure),balloon catheter 210 pushes against an inner surface of stent 220,causing stent 220 to expand to match the diameter of bore 625 formed bygrooves 620 a and 620 b. However, since half washers 650 extend intogrooves 620 a and 620 b, the proximal and distal ends of stent 220cannot expand to the same diameter as the rest of the stent 220 (e.g.,to the diameter of bore 625).

Accordingly, stent 220 has a profile after molding in which at least aportion of its proximal and distal ends are tapered inwards. The taperedinward edges facilitate smooth communication of stent 220 through apatient's vasculature without substantially limiting the ability ofstent 220 to bend around curvatures in the vasculature. Further, thetapered ends tend to grip the balloon catheter 210 better than untaperedends, inhibiting or preventing stent 220 from disengaging from ballooncatheter 210 before it is deflated.

Half 610 a includes a first member 630 of a barrel locking mechanism.Half 610 b includes a second and third member of the barrel lockingmechanism 640 a and 640 b. Member 630 acts in combination with members640 a and 640 b to lock mold 600 after placement of balloon catheter 210and stent 220 into grooves 610 a or 610 b and closing mold 600. Thebarrel locking mechanism inhibits or prevents mold 600 from opening whenballoon catheter 210 is expanding.

In alternative embodiments of the invention, different lockingmechanisms can be used. Further, halves 610 a and 610 b need not becoupled together via hinge 615.

FIG. 7 is a diagram illustrating a cross section of mold 600. Closingmold 600 forms bore 625 in which a mounted stent 220 is disposed.Mounted stent 220 is aligned with half washers 650 such that the distalend of the stent 220 is in alignment with a first pair of half washers650 and the proximal end is in alignment with a second pair of halfwashers 650. Half washers 650 on the same mold half are spaced apart ata length equal to about the length of mounted stent 220. Half washerscan extend several thousandths of an inch into the bore of the mold 600(e.g., about 0.002 to about 0.005 inches, or more narrowly about 0.003to about 0.004). Half washers can have a width of about 0.5 mm to about4 mm or slightly less than half the length of the stent.

In an embodiment of the invention, mold 600 includes only a single pairof half washers 650 that are positioned at one end of stent 220,preferably the leading edge of stent 220 (i.e., the edge of stent 220that faces the direction of travel during installation of stent 220).Accordingly, stent 220 would have a single tapered end that wouldfacilitate deliverability of stent 220.

Once stent 220 is disposed within bore 625 of closed mold 600, ballooncatheter 210 is heated and expanded. Specifically, balloon catheter 210is heated up to about 190°

F. to soften balloon catheter 210, thereby causing expansion (referredto as thermogripping). Internal pressure is supplied to the ballooncatheter 210 to cause further expansion. Specifically, about 120 PSI toabout 330 PSI, or more narrowly about 150 PSI to about 290 PSI, can beapplied to cause expansion of catheter 210.

Expansion of balloon catheter 210 causes balloon catheter 210 to pressagainst the inner diameter of stent 220. Expansion of balloon catheter210 causes a majority of stent 220 to expand to the diameter of bore 625of mold 600. Half washers 650 prevent ends of stent 220 aligned with thehalf washers 650 from expanding to the diameter of bore 625 of mold 600.As the ends of the stent 220 press against the half washers 650, theends of the stent 220 are prevented from expanding, thereby yielding astent profile with inward tapered ends.

In one embodiment, a mold bore may have a proximal section taperinginward to a proximal end of the mold bore and a distal section taperinginward to a distal end of the mold bore. The tapered sections may beadapted to mold tapered sections of the stent that improve theattachment of the stent to the delivery system and that facilitate thedelivery of the mounted stent into and through a bodily lumen. In anembodiment, the mold bore may taper inward relatively uniformly betweena proximal section and a distal section.

FIG. 8 is a diagram illustrating a mold 800 according to anotherembodiment of the invention. Mold 800 is substantially similar to mold600 except that mold 800 includes a mold block 850 rather than washers650. Specifically, mold 800 includes two mold halves 810 a and 810 bcoupled together via a hinge 815. Half 810 a includes a groove 820 ahaving a mold block 850 and half 810 b includes a groove 820 b having amold block 850. A barrel lock mechanism 830 is coupled to half 810 a.Mechanism 830 acts in combination with barrel lock mechanisms 840 a and840 b that are coupled to half 810 b, to lock mold 800 shut afterplacement of a stent 520 within.

FIG. 9 is a diagram illustrating an axial cross section of a mold 800that may mold stent 300 depicted in FIG. 3. Mold block 850 (and aresulting stent 300 shown in FIG. 3 after balloon catheter 220 expands)has an arrow-like shape in which a mold bore 855 of mold block 850tapers inward relatively uniformly from a proximal to a distal end ofbore 855. The diameter of mold bore 855 of mold block 850 graduallyincreases from a distal end to a proximal end.

Delivery of the stent may be facilitated by having the distal end as theend of the stent that faces the direction of delivery. In oneembodiment, the distal end or leading end may have a diameter of about0.038 inches. The diameter may increase to a point proximate to theproximal end to a diameter of about 0.041 inches (e.g., at about 5.5 mmfrom the leading end in a 6 mm stent). At the proximal end, the diametermay taper off from about 0.041 inches to about 0.038 inches (from about0.5 mm from the proximal end in a 6 mm stent).

In other embodiments, the mold bore may taper inward relativelyuniformly from an intermediate point between a proximal end and a distalend to the proximal end. The mold bore may also taper inward relativelyuniformly from the intermediate point to the distal end.

FIG. 10 is a diagram illustrating a cross section of a mold 1000according another embodiment of the invention for molding stent 410 inFIG. 4. The mold 1000 is substantially similar to the mold 600 exceptthat mold block 650 is replaced with a mold block 1050. Bore 1055 ofmold block 1050 tapers inward from approximately a midpoint along bore1055 toward both a distal and proximal end of bore 1055. The slope ofthe taper is such that expansion of a stent 420 in mold 1000 yields astent 420 having a smaller diameter at the proximal and distal ends witha gradually increasing diameter to a maximum diameter at the middle ofstent 420.

In a further embodiment, a mold bore of a mold member may have a sectionwith a cross-section that oscillates in size between a proximal sectionand a distal section. The oscillating cross section may be configured tomold a stent mounted on a delivery system to have an oscillating crosssection. The oscillating cross section of the stent may improveflexibility of the mounted stent during delivery.

FIG. 11 is a diagram illustrating a cross section of a mold 1100according another embodiment of the invention for molding stent 520 inFIG. 5. Mold 1100 is substantially similar to the mold 600 except that amold block 1150 replaces mold block 650. Mold block 1150 isapproximately the length of stent 520. Bore 1155 of mold block 1150 hasa diameter than varies along its length with larger diameter sectionsalternating with smaller diameter sections. As shown in FIG. 11, theinner surfaces of mold block 1150 have a wave-like profile. For example,in profile, the mold block 1150 can take the form of a sine wave. In anembodiment of the invention, bore 1155 of mold block 1150 can have threecrests and four troughs, with troughs occurring at the proximal anddistal ends.

In FIG. 11, mold block 1150 matches the length of the stent (e.g., about6 mm) and features three crests and four troughs, wherein two troughsare aligned with the proximal and distal ends of the stent 520.Expansion of balloon catheter 210 causes stent 520 to take the shape ofbore 1155 of mold block 1150, e.g., the stent 520 develops a waveprofile, which secures stent 520 to balloon catheter 210 whilemaintaining flexibility and facilitating deliverability. The heightvariation between crests and troughs is a few thousands of an inch,e.g., about 0.001 to about 0.005 inches, or more narrowly, about 0.003to about 0.004.

FIG. 12 is a flowchart illustrating a method 1200 of gripping a stent ona catheter according to an embodiment of the invention. First, a stentis mounted (1210) on a catheter, as is known to those of ordinary skillin the art. The mounted stent in then placed (1220) in a groove of amold (e.g., the molds 600, 800, 1000 or 1100) and aligned with thewashers or blocks. The mold is then closed (1230) and locked. Heat isthen applied (1240) to the balloon catheter 210 to cause the ballooncatheter 210 to soften and therefore more easily expand. In anembodiment of the invention, the heat can reach up to about 190° F. Theballoon catheter 210 is then expanded (1250) by applying internal airpressure, e.g., about 120 PSI to about 330 PSI, or more narrowly about150 PSI to about 290 PSI. During expansion, the balloon catheter 210expands and presses into the stent, causing the stent to expand untilthe stent matches the diameter of the bore of the mold. The stent thentakes on the shape of the mold. The mounted stent is then removed (1260)from the mold after the mold is unlocked.

In some embodiments, heat may facilitate expansion of the stent. Heatmay be applied to the device and/or the delivery system prior to and/orduring expanding the device. Heat may be applied by pumping heated fluidinto a delivery system, such as balloon catheter. Alternatively heatapplied by blowing a heated inert gas (e.g., air, nitrogen, oxygen,argon, etc.) onto the device and/or the delivery system.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art thatchanges and modifications can be made without departing from thisinvention in its broader aspects. Therefore, the appended claims are toencompass within their scope all such changes and modifications as fallwithin the true spirit and scope of this invention.

What is claimed is:
 1. A radially expandable stent mounted on a deliverysystem, the stent comprising: a proximal section tapered inward to aproximal end of the stent and a distal section tapered inward to adistal end of the stent, the tapered sections being adapted to improvethe attachment of the stent to the delivery system and to facilitate thedelivery of the mounted stent into and through a bodily lumen.
 2. Thestent of claim 1, wherein the stent comprises a biostable and/orbiodegradable polymer.
 3. The stent of claim 1, wherein the stentcomprises a profile that tapers inward relatively uniformly between theproximal section and the distal section.
 4. The stent of claim 1,wherein the proximal section tapers inward relatively uniformly from anintermediate point between the proximal end and the distal end to theproximal end, and wherein the distal section tapers inward relativelyuniformly from the intermediate point to the distal end.
 5. The stent ofclaim 1, wherein the delivery system comprises a balloon catheter.